<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        div{
            width: 400px;
            height: 200px;
            background-color: red;
            margin: auto;
        }


    </style>
</head>
<body>
<div></div>
</body>
</html>